A 29-year-old man who smashed windows at West Australian Premier Colin Barnett's office with a hammer and graffitied them with the words "ego maniac" has been fined $1500 and ordered to pay thousands of dollars in repairs.

Adrian Kendall Thomas pleaded guilty in the Perth Magistrates Court on Tuesday to two counts of criminal damage or destruction of property.

"Egomaniac" was daubed in red across the office windows. Photo: Nine News Perth

The court heard Thomas, who has Aspergers and finds it difficult to regulate his emotions, was mad at the Premier for his environmental policies and gave staff at the office safety glasses before smashing windows.

Mr Barnett, who has recently been criticised over his policy to cull large sharks in WA waters, was not in the office at the time.

Thomas requested a spent conviction because a record would affect his employment, but chief magistrate Steven Heath said with the amount of planning involved in the vandalism, he did not think it was appropriate.

"You knew what you were going to do was wrong," he said.

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Thomas replied it was not planned and would not happen again.

"It was an emotional outburst and completely out of character," he said.

Thomas was fined $1000 for the windows and $500 for the graffiti.

He was also ordered to pay more than $4900 in repairs and court costs.

Outside court, Thomas apologised for his "juvenile" behaviour but also questioned whether the Premier was fit to hold the position.

"My frustration was born, however, by a ridiculous decision at the end of a long list of ridiculous decisions made by Colin Barnett," he said.pr